3. Use Table 5.2 (below), and the water stability (potential vs. pH) graph (belo

Question

3. Use Table 5.2 (below), and the water stability (potential vs. pH) graph (below), to determine whether the following would be stable in water. Explain. For cases in which the species would be unstable, indicate the water-derived product that would form a. Co3+ at pH= 0 (E1/2(C03-/Co-*)= +1 .92 V) b. Zn° at pH-2 c. Zn2* at pH-2 d. [IrCl]at pH- 14 e. [IrClat pH- 14 f. Fe2+ at pH=0 With overotential EIV Table 5.2 Selected standard potentials at 298 K; further values are included in Resource section 2 Couple F2(g) +2e- 2F (aq) O2/H2O E IN 0.8 +2.87 +1.76 +0.4 lNatural ce'"(aq) + e- Ce3 + (aq) +1.51 +1.36 +1.23 +0.87 +0.77 +0.60 +0.54- +0.36 +0.22 , waters Cl2(g) + 2 e- 2 cr (aq) 02(g) + 4 H+ (aq) + 4 e- 2 H20( 0.4 Fe3(a)eFe (aq) [PtCl/-(aq) + 2 e- Pt(s) + 4 Cl-(aq) 0.8 (aq) + 2 e- 31-1 (aq) [Fe(CN)6]3-(aq) + e- [Fe(CN) 4-(aq) AgCI(s) e Ag(s)+CI (aq) 2H+(aq) + 2e- H2(g Agl(s) + e- Ag(s) + I-(aq) Zn2+ (aq) + 2 e- Zn(s) Al3+ (aq) + 3 e- Al(s) Ca2+ (aq) +2 e- Ca(s) Li+(aq) + e--+ Li(s) overpotential -0.15 -0.76 0 2 4 6 8 10 12 14 -2.84 -3.04 pH

Explanation / Answer

a) Co3+ would be unstable at pH=0 because it has more reduction potential value hence it will reduce to Co2+

b) Zn0 is unstable at pH=2 , willeasyly oxidize to produce Zn2+

c) Zn2+ is stable at pH=2, since at pH=2 water can facilitate H+ ions wich will protect Zn2+

d) [IrCl6]2- is unstable at pH=14, due to presence of OH- ions

e) [IrCl6]3- is Stable at pH=14

f) Fe2+ stable at pH=0 due to presence of acis nature

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